Are 2 Biosimilars to the Same Originator Product Biosimilar to Each Other?

In Europe, several manufacturers are marketing approved biosimilars to the same originator product. In fact, 7 manufacturers compete for the biosimilar filgrastim market, 5 biosimilar versions of epoetin are sold, and 3 biosimilars of infliximab seek marketshare from Remicade®. In the US, this situation is not a reality yet. It will be one day, however, and it raises a couple of important questions.

We know that the biosimilars are not exactly the same structurally as the originator products, but how similar may they be to each other? In other words, at some point, payers will prefer one biosimilar version of filgrastim over another one, as some do currently with Zarxio® versus Neupogen®. We can assume that with 3 filgrastim biosimilars sold in the US, payers will seek to leverage 1 against the others and make it their preferred or only available form of filgrastim available. However, is another manufacturer’s version of filgrastim biosimilar to Zarxio? We can also assume that the new manufacturer’s product has received US Food and Drug Administration approval through testing for comparability only with the originator product—not against Zarxio. How about compared with Teva’s product tbo-filgrastim (a follow-on biologic, not a biosimilar according to the regulatory and statutory rules)?

What does this mean for switching products, much less interchangeability? Is one biosimilar interchangeable with another? Based on what we know about the FDA, the answer is likely no, as the agency seems to be having difficulty devising interchangeability guidelines for a biosimilar and its originator product.

Why is this important? Consider the patient with Crohn’s disease in 2019 who changes health plans. The patient was receiving biosimilar A, and the new plan covers only biosimilar B. Maybe he or she needs to enroll in a new plan in 2020, and the reverse is true. Regardless of whether we like it, that patient may be unintentionally providing real-world evidence of interchangeability.